Ring opening reactions of 2-trialkylsilylaziridines

Abstract

2-Trialkylsilylaziridines do not readily undergo nucleophilic ring opening without electrophilic assistance. In the presence of strong acids protonation at the nitrogen is followed by nucleophilic attack α to the silicon. With non-nucleophilic counterions, the protonated aziridine can be obtained. N-Alkylation gives the aziridinium salt, which also undergoes α-cleavage. However, the presence of a 3-phenyl substituent gives a stable aziridinium salt that undergoes nucleophilic attack β to the silicon. Reaction of 2-trialkylsilylaziridines with trialkylsilyl halides usually leads to α-cleavage, however, desilylation to give the enamine is also observed. Fluorodesilylation of the 2-trialkylsilylaziridine is not straightforward and only occurred readily when a 2-ethoxycarbonyl group was present. Fluorodesilylation followed by attack on a carbonyl was only observed when very dry samples of fluoride ions were employed.